The question is not the frequency, but the edge rate. For a 1 PPS signal, how fast a rise time do you need? Do you want to know the time of the edge to 1/100 second? one microsecond? one nano-second? A few pico-seconds?
If you want to know the time of the edge to one nano-second, then you need a driver that can push sine-waves at over a few GHz. Not 10 MHz. --- Graham / KE9H == On Sat, Mar 7, 2015 at 7:58 AM, Didier Juges <shali...@gmail.com> wrote: > Martyn, if you only need 1Hz, I recommend you use a MOSFET driver like the > MIC4420 series or the UCC27531, powered from 10V with a 50 ohm output > resistance. These parts have several A current capability, 18V or more max > VCC and are designed to drive capacitive loads (large MOSFET gate > capacitance). It would not work at 10MHz (because of propagation delay and > self heating), but at lower frequencies, they work very well. > The UCC27531 has lower propagation time and comes in an SOT-23 package, the > others are available in DIP-8 and SO-8. > > Didier KO4BB > > On Thu, Mar 5, 2015 at 3:59 PM, Martyn Smith <mar...@ptsyst.com> wrote: > > > Hello, > > Thanks for all the feedback. > > I should explain. I have an existing product that uses the 74AC14. > > I have a customer who needs 5V into 50 ohm and can’t wait for the > > competitive product that does this, or for me to re-design my unit. > > So I have been looking for a quick fix. > > I got excited when I found the SN74AS1004AD which has the exact same > > function and pin out but delivers 48 mA per channel. > > While one output did give me 0-3.0 V into 50 ohm, combining them, as we > do > > for the 74AC, actually produced worse results. > > Maybe the output driver is different. > > Anyway I’ve managed to get 0-4.8V by jacking up the supply voltage to 5.7 > > V for the 74AC14 and making the three 47 ohm resistors 0 ohm. > > Risetime < 4 ns. > > Basically to ideas that TimeNuts gave me. > > I’m just worried the IC may die after a few months. But since the > > customer will only use it at 1 Hz and hopefully 50:50 duty, or less, I > hope > > to get away with it. > > Of course if he removes the input and the outputs are on high, then that > > may be a problem. > > BTW, the reason he wants this high voltage is because he is driving a > very > > long cable from the distribution amp to the actual receiver. > > Anyway I have an IC on test for a week to make sure it lasts. > > Regards > > Martyn > > > > > > Today's Topics: > > > > 1. Re: 50 ohm Driver (Bob Albert) > > 2. Re: 50 ohm Driver (Graham / KE9H) > > 3. Re: 50 ohm Driver (Tom Van Baak) > > 4. Re: 50 ohm Driver (Hal Murray) > > 5. Re: 50 ohm Driver (Dan Kemppainen) > > 6. Re: Trimble Thunderbolt NMEA ? (Didier Juges) > > 7. Re: 50 ohm Driver (Bob Camp) > > 8. Re: 50 ohm Driver (Charles Steinmetz) > > 9. Re: new tdc from Texas (Angus) > > 10. Re: new tdc from Texas (Attila Kinali) > > > > > > ---------------------------------------------------------------------- > > > > Message: 1 > > Date: Wed, 4 Mar 2015 16:49:11 +0000 (UTC) > > From: Bob Albert <bob91...@yahoo.com> > > To: Discussion of precise time and frequency measurement > > <time-nuts@febo.com> > > Subject: Re: [time-nuts] 50 ohm Driver > > Message-ID: > > <1276775018.2671439.1425487751520.javamail.ya...@mail.yahoo.com> > > Content-Type: text/plain; charset=UTF-8 > > > > 5V into 50 Ohms means 100 mA. Perhaps you need a medium power transistor > > amplifier or opamp. > > Bob > > > > > > On Wednesday, March 4, 2015 6:09 AM, Martyn Smith < > mar...@ptsyst.com> > > wrote: > > > > > > Hello, > > > > A quick question. > > > > My output driver for a simple amplifier. > > > > I use three gates (in parallel with resistors) from a 74AC14 to give me > > about 0-3.2V into 50 ohm. > > > > I want to have a driver that gives me a full 0-5V (at least 0-4.5V) swing > > into 50 ohms. > > > > Can anyone recommend an IC that can delivery this. > > > > But it needs to have similar jitter performance to the 74AC14. > > > > I use it up to 10 MHz. > > > > Best Regards > > > > Martyn > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > > > > > > > > ------------------------------ > > > > Message: 2 > > Date: Wed, 4 Mar 2015 12:16:02 -0600 > > From: "Graham / KE9H" <ke9h.gra...@gmail.com> > > To: Discussion of precise time and frequency measurement > > <time-nuts@febo.com> > > Subject: Re: [time-nuts] 50 ohm Driver > > Message-ID: > > <capyj-yxrlkw6y-poglqwjss+mehm6ifc+etyb-mcczkhjpw...@mail.gmail.com> > > Content-Type: text/plain; charset=UTF-8 > > > > Building on top of John's comments, if you are using a logic gate, look > at > > the > > maximum output (pull up) current per pin, set the series resistor so that > > this > > current is not exceeded into a short, then also see if there is a maximum > > total > > current draw for all gates combined, or some power input pin, and do not > > exceed > > that. > > > > You can also look at switching the termination resistor from a simple 50 > > Ohm > > resistor to ground, to a "Thevenin" load, which is 100 Ohms from +V to > the > > load point, > > and another 100 Ohm resistor from the load point to ground. This way you > > still have a 50 Ohm termination, but only draw one half the DC current. > > In the event of no input, the receiver voltage will go to half scale. > Make > > sure your system will not misbehave when this happens. > > > > Alternate driver is to use a video line driver with sufficient bandwidth. > > > > --- Graham / KE9H > > > > == > > > > On Wed, Mar 4, 2015 at 7:54 AM, John Ackermann N8UR <j...@febo.com> > wrote: > > > > > One comment on the parallel AC gate approach. It may not be directly > > > applicable to Martyn's issue, but there is a common confusion about the > > > value of the summing resistors. > > > > > > Per Tom Clark, who came up with the idea, they are *not* intended to > > > provide a near-end line termination to 50 ohms, but are simply there to > > > protect the paralleled devices if the gates have slightly different > > delays > > > (in which case one gate could end up sinking the other two). > > > > > > So, the commonly used 47 ohm value isn't magic. You can use a lower > > > value, and thus get more voltage at the far end. I haven't > experimented > > to > > > see how far you can take that idea before destroying gates. > > > > > > John > > > ---- > > > > > > On 3/4/2015 5:26 AM, Martyn Smith wrote: > > > > > >> Hello, > > >> > > >> A quick question. > > >> > > >> My output driver for a simple amplifier. > > >> > > >> I use three gates (in parallel with resistors) from a 74AC14 to give > me > > >> about 0-3.2V into 50 ohm. > > >> > > >> I want to have a driver that gives me a full 0-5V (at least 0-4.5V) > > swing > > >> into 50 ohms. > > >> > > >> Can anyone recommend an IC that can delivery this. > > >> > > >> But it needs to have similar jitter performance to the 74AC14. > > >> > > >> I use it up to 10 MHz. > > >> > > >> Best Regards > > >> > > >> Martyn > > >> > > >> _______________________________________________ > > >> time-nuts mailing list -- time-nuts@febo.com > > >> To unsubscribe, go to https://www.febo.com/cgi-bin/ > > >> mailman/listinfo/time-nuts > > >> and follow the instructions there. > > >> > > >> _______________________________________________ > > > time-nuts mailing list -- time-nuts@febo.com > > > To unsubscribe, go to https://www.febo.com/cgi-bin/ > > > mailman/listinfo/time-nuts > > > and follow the instructions there. > > > > > > > > > ------------------------------ > > > > Message: 3 > > Date: Wed, 4 Mar 2015 10:20:45 -0800 > > From: "Tom Van Baak" <t...@leapsecond.com> > > To: "Discussion of precise time and frequency measurement" > > <time-nuts@febo.com> > > Subject: Re: [time-nuts] 50 ohm Driver > > Message-ID: <231A4CB7D0CB45CAAF6A3015A4900374@pc52> > > Content-Type: text/plain; charset="utf-8" > > > > Martyn -- the 74AC spec allows Vcc to go up to 6.0 VDC (absolute max is > > 7.0 VDC) so that might help you meet your 4.5 VDC goal, especially if > this > > is for play and not a product. Pick the resistors and use more than 3 > gates > > if necessary. Note the peak current spec is 50 mA per gate. Not sure what > > the combined gate current limit is; there is a package thermal limit. You > > also have to decide if you want some level of short-circuit protection or > > if you can always assume 50R termination. > > > > John -- have you tried long duration output shorts on the TADD-2? I > > figured that was also a reason for each gate having its own resistor. > > > > /tvb > > > > > > > > ------------------------------ > > > > Message: 4 > > Date: Wed, 04 Mar 2015 12:03:16 -0800 > > From: Hal Murray <hmur...@megapathdsl.net> > > To: Discussion of precise time and frequency measurement > > <time-nuts@febo.com> > > Cc: hmur...@megapathdsl.net > > Subject: Re: [time-nuts] 50 ohm Driver > > Message-ID: > > <20150304200316.6afbc406...@ip-64-139-1-69.sjc.megapath.net> > > Content-Type: text/plain; charset=us-ascii > > > > > > j...@febo.com said: > > > Per Tom Clark, who came up with the idea, they are *not* intended to > > > provide a near-end line termination to 50 ohms, but are simply there to > > > protect the paralleled devices if the gates have slightly different > > delays > > > (in which case one gate could end up sinking the other two). > > > > Is that a real problem? How far off can the prop delay be for 2 gates on > > the > > same chip? > > > > I seem to remember reading something saying it was OK to just wire them > up > > in > > parallel. It could have been an app note, or it could have been a rumor > on > > usenet. > > > > -- > > These are my opinions. I hate spam. > > > > > > > > > > > > ------------------------------ > > > > Message: 5 > > Date: Wed, 04 Mar 2015 15:57:56 -0500 > > From: Dan Kemppainen <d...@irtelemetrics.com> > > To: time-nuts@febo.com > > Subject: Re: [time-nuts] 50 ohm Driver > > Message-ID: <54f771d4.4010...@irtelemetrics.com> > > Content-Type: text/plain; charset=utf-8; format=flowed > > > > Hi, > > > > Correct me if I'm wrong but being that AC series gates are MOS devices, > > isn't there inherent current limiting in the MOS junction itself? I > > would think that for the few nanoseconds of skew across gates the tens > > of ohms of junction resistance would make 'shoot through' negligible in > > terms of heating and gate damage. > > > > Of course, a TTL device would be a completely different story and I > > would fully expect summing or balancing resistor would be needed there. > > > > Does anyone have further input regarding paralleling MOS logic devices? > > > > Dan > > > > > > > > > One comment on the parallel AC gate approach. It may not be directly > > > applicable to Martyn's issue, but there is a common confusion about the > > > value of the summing resistors. > > > > > > Per Tom Clark, who came up with the idea, they are*not* intended to > > > provide a near-end line termination to 50 ohms, but are simply there to > > > protect the paralleled devices if the gates have slightly different > > > delays (in which case one gate could end up sinking the other two). > > > > > > So, the commonly used 47 ohm value isn't magic. You can use a lower > > > value, and thus get more voltage at the far end. I haven't > experimented > > > to see how far you can take that idea before destroying gates. > > > > > > John > > > > > > ------------------------------ > > > > Message: 6 > > Date: Wed, 04 Mar 2015 17:44:09 -0600 > > From: Didier Juges <shali...@gmail.com> > > To: Discussion of precise time and frequency measurement > > <time-nuts@febo.com> > > Subject: Re: [time-nuts] Trimble Thunderbolt NMEA ? > > Message-ID: <ef4edc38-c96b-402f-ab2f-9ac273ab3...@gmail.com> > > Content-Type: text/plain; charset=UTF-8 > > > > The code is in C and Silabs has small dev kits (Toolsticks) that cost $10 > > to which you need to add $18 for the programming dongle. A little more > > expensive than an Arduino, or less, depending on where you buy it... > > > > To that you need to add a MAX232 (or two serial-TTL adapters at $4 each > or > > so on ebay) and you are in business. > > > > Total cost about the same as a dedicated GPS receiver with antenna and > > NMEA output. Choose your poison :) > > > > Didier KO4BB > > > > > > On March 3, 2015 10:23:56 PM CST, Chris Albertson < > > albertson.ch...@gmail.com> wrote: > > >Is the code in C? If so I bet it would run on some development board. > > >No > > >need to make custom PCBs. > > > > > >On Tue, Mar 3, 2015 at 5:00 AM, Didier Juges <shali...@gmail.com> > > >wrote: > > > > > >> Tim, > > >> > > >> It shouldn't be too hard to modify the code for my Thunderbolt > > >monitor to > > >> make it into a TSIP->NMEA converter. The last version of the kit has > > >a uC > > >> with two serial ports. I m out of the kits at the moment but I have a > > >few > > >> spare boards left over. > > >> > > > > > >-- > > > > > >Chris Albertson > > >Redondo Beach, California > > >_______________________________________________ > > >time-nuts mailing list -- time-nuts@febo.com > > >To unsubscribe, go to > > >https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > >and follow the instructions there. > > > > -- > > Sent from my Motorola Droid Razr HD 4G LTE wireless tracker while I do > > other things. > > > > ------------------------------ > > > > Message: 7 > > Date: Wed, 4 Mar 2015 18:47:13 -0500 > > From: Bob Camp <kb...@n1k.org> > > To: Discussion of precise time and frequency measurement > > <time-nuts@febo.com> > > Subject: Re: [time-nuts] 50 ohm Driver > > Message-ID: <efc260cc-caf3-4021-8ef9-27540ae57...@n1k.org> > > Content-Type: text/plain; charset=utf-8 > > > > Hi > > > > If you want to drive out of a 50 ohm source into your 50 ohm load *and* > > get 5V into the load … that’s a fancy amp. 10V power and some careful > > work to get it going. > > > > If you just want to get roughly 5V into a 50 ohm load, then it’s a matter > > of how > > many gates you decide to parallel. If you go with “32 ma” drivers, you > > should > > be able to get it done with 8 of them in parallel. Drive them all off of > a > > single > > dedicated fast gate that’s on the same supply. Probably best to stuff > > a 20 or 30 ohm resistor in series with each of the outputs. If it’s *got* > > to > > be a full 5V, don’t use the resistors. > > > > Bob > > > > > On Mar 4, 2015, at 5:26 AM, Martyn Smith <mar...@ptsyst.com> wrote: > > > > > > Hello, > > > > > > A quick question. > > > > > > My output driver for a simple amplifier. > > > > > > I use three gates (in parallel with resistors) from a 74AC14 to give me > > about 0-3.2V into 50 ohm. > > > > > > I want to have a driver that gives me a full 0-5V (at least 0-4.5V) > > swing into 50 ohms. > > > > > > Can anyone recommend an IC that can delivery this. > > > > > > But it needs to have similar jitter performance to the 74AC14. > > > > > > I use it up to 10 MHz. > > > > > > Best Regards > > > > > > Martyn > > > > > > _______________________________________________ > > > time-nuts mailing list -- time-nuts@febo.com > > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > and follow the instructions there. > > > > > > > > ------------------------------ > > > > Message: 8 > > Date: Wed, 04 Mar 2015 19:44:29 -0500 > > From: Charles Steinmetz <csteinm...@yandex.com> > > To: Discussion of precise time and frequency measurement > > <time-nuts@febo.com> > > Subject: Re: [time-nuts] 50 ohm Driver > > Message-ID: <20150305034434.iyvem...@smtp12.mail.yandex.net> > > Content-Type: text/plain; charset="us-ascii"; format=flowed > > > > > > >Is [one gate sourcing or sinking current into paralleled gates that > > >don't switch at > > >exactly the same time] a real problem? How far off can the prop > > >delay be for 2 > > >gates on the same chip? > > > > > >I seem to remember reading something saying it was OK to just wire them > > up in > > >parallel. It could have been an app note, or it could have been a rumor > > on > > >usenet. > > > > Most manufacturers sanction direct paralleling of gates on the same > > chip (and forbid any paralleling, ballasted or otherwise, of outputs > > from different chips). However, there are other considerations > > (short-circuit protection, maximum output current rating per gate, > > maximum supply and/or ground current rating per package, maximum > > power dissipation, etc.). Good design practice is to put series > > resistors on each gate output that will prevent any of these ratings > > from being exceeded into a short circuit to ground or to Vcc. For > > HC, AC, NC7NZ, and NC7SZ, the per-gate output current rating is +/- > > 24 (or 25) mA, which suggests that each gate should have a 200 ohm > > series resistor -- but you need to check all of the other ratings > > mentioned above for the chip you use, to make sure they won't be > violated. > > > > Unfortunately, if the load is 50 ohms to ground, pulling it to even > > 4.5v from a 5v logic supply requires a source resistance of only 5.6 > > ohms, or 36 parallel gates each with 200 ohms in series (this assumes > > that the gates can pull all the way to 5v while delivering rated > > current, which they can't -- so the reality is even worse). You can > > make things a little better by terminating the output into 50 ohms to > > 1/2 Vcc (i.e, the center of a voltage divider with 100 ohms to Vcc > > and 100 ohms to ground), but (i) it only gets a little better, and > > (ii) now it won't pull all the way to ground. > > > > All that said, why do you want to generate a high-current square > > wave, anyway? If you're distributing a frequency standard, it is > > much better to distribute a sine wave (you don't have to worry about > > the harmonics being skewed, and there is exponentially less of a > > problem with it radiating and getting into every radio and other > > sensitive electronic device in your house and the other houses on the > > block). > > > > Best regards, > > > > Charles > > > > > > > > > > > > ------------------------------ > > > > Message: 9 > > Date: Thu, 05 Mar 2015 01:27:23 +0000 > > From: Angus <not.ag...@btinternet.com> > > To: Discussion of precise time and frequency measurement > > <time-nuts@febo.com> > > Subject: Re: [time-nuts] new tdc from Texas > > Message-ID: <uu9ffapgkl5t7qnv73m9v7j2ba5mttl...@4ax.com> > > Content-Type: text/plain; charset=us-ascii > > > > Hi, > > > > I've not seen any mention of anything other than the TDC1000. > > > > I was a bit surprised that they went down the less-integrated route > > and separated the TDC, but it turns out that for a lot of the sort of > > things they designed it for, a uC provides good enough timing itself, > > and no extra TDC is needed at all. > > > > I see that Acam have released a bit more info on their new GP30, > > although no data sheet yet. It quotes typical LSB of 11ps, and rms > > noise of 1.2 LSB, which is quite an improvement on the GP22. > > It would just be good if they offered a simple online way of getting > > low volumes of them - I suspect that the specialist distributors would > > be just as happy as the customers would be! > > > > Angus. > > > > > > On Tue, 03 Mar 2015 15:43:25 -0800, you wrote: > > > > >Hi Angus: > > > > > >Do you know if they have an IR pulse front end which would be more > > interesting than the ultrasonic front end? > > > > > >Mail_Attachment -- > > >Have Fun, > > > > > >Brooke Clarke > > >http://www.PRC68.com > > >http://www.end2partygovernment.com/2012Issues.html > > >http://www.prc68.com/I/DietNutrition.html > > >Angus wrote: > > >> In case anyone is interested, the full data sheet is on the TI site > > >> now, although I didn't see any actual IC's yet other than the ones in > > >> the eval boards. > > >> > > >> Angus. > > >> > > >> > > >> On Tue, 17 Feb 2015 21:24:08 -0200, you wrote: > > >> > > >>> Initial datasheet: > > >>> > > >>> http://www.ti.com/lit/ds/symlink/tdc7200.pdf > > >>> > > >>> EVM: > > >>> > > >>> http://www.ti.com/tool/tdc1000-tdc7200evm > > >>> > > >>> Seems good... what do you think? > > >>> > > >>> Daniel > > >>> _______________________________________________ > > >>> time-nuts mailing list -- time-nuts@febo.com > > >>> To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > >>> and follow the instructions there. > > >> _______________________________________________ > > >> time-nuts mailing list -- time-nuts@febo.com > > >> To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > >> and follow the instructions there. > > >> > > > > > >_______________________________________________ > > >time-nuts mailing list -- time-nuts@febo.com > > >To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > >and follow the instructions there. > > > > > > ------------------------------ > > > > Message: 10 > > Date: Thu, 5 Mar 2015 08:56:23 +0100 > > From: Attila Kinali <att...@kinali.ch> > > To: Discussion of precise time and frequency measurement > > <time-nuts@febo.com> > > Subject: Re: [time-nuts] new tdc from Texas > > Message-ID: <20150305085623.cb5218ab541d5ffaf13dc...@kinali.ch> > > Content-Type: text/plain; charset=US-ASCII > > > > On Thu, 05 Mar 2015 01:27:23 +0000 > > Angus <not.ag...@btinternet.com> wrote: > > > > > I've not seen any mention of anything other than the TDC1000. > > > > > > I was a bit surprised that they went down the less-integrated route > > > and separated the TDC, but it turns out that for a lot of the sort of > > > things they designed it for, a uC provides good enough timing itself, > > > and no extra TDC is needed at all. > > > > I think the main application TI intended it for is for ultrasonic > > flow meeters (like [1]). There you have quite small and bounded > > start-stop delays. With this they can get into the growing electronics > > for low energy building market. > > > > In contrast to that, the Acam devices seem to be general purpose TDCs > > > > > > Attila Kinali > > > > > > [1] http://www.shk-profi.de/imgs/52579203_0d4dd378d4.jpg > > -- > > < _av500_> phd is easy > > < _av500_> getting dsl is hard > > > > > > ------------------------------ > > > > Subject: Digest Footer > > > > _______________________________________________ > > time-nuts mailing list > > time-nuts@febo.com > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > > ------------------------------ > > > > End of time-nuts Digest, Vol 128, Issue 5 > > ***************************************** > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.